Radio beacon



i Y imipucafioh March 30,1938, seriarNo.

- In France April 2, 1937 V zj ol im's; (01. 250-711) 'I lrie present invention. has as .itsobj eot the obviation of certain difliculties. attendant upon 'the taking of bearings orin' direction-finding"by stations. Twochief methodsareknowniin the art, name.-;

-I: E D;. PATENT O FFICI E" 1 pagnie' Ge'neraIe de Telegraphic sans Fil; a corporationof France a :v

2 theaid of signals transmitted from. radioi beacon ly, the interlocked keying .011 A--:-N method iinF Whichaisudden change istmade vin transmitting fromv-one; radiation diagram or characteristic to anotheri characteristic as in crossed coil beacons working-with long waves customary in the U..S: A., and ltheiimethod predicated. upon a radio-beacon transmitting a diagram fol-characteristic of cardioidishape...:

course: is outlined (froml4 170115 "degrees," forin- 'stance,-with a; standard receiver), and the ratio of the "change in the received signalintensity due course defined by the radio beacon. The signal corresponding to one radiationdiagram increases where, sharp courses are, to ibe' outlined.

narsjby reversal of-jthe'j phase of" one oft-h while 'that corresponding to the other decreases untilionly one signal having distinctofi and on periods is heard'.- The keying depth therefore be comes v110 0 percent when the departure from the course. amounts to;45 degrees so that the decreasev inolearness ofv the signals'indicates quite dis- V tinctly the .fact that a 'course'or pathis being approached.:;:

.In the second methodis tosay, in .direc- 'tion-finding using a'cardioid type field distribution, sign aling takes place by alternately reversing' the phase of the-fieldradiatedxby one of the twogtransmitting aerialsfwith respectto the phase o'fzztherfield radiatedbythe other. The path de I finedgbythexbeacon then is characterizediby a re' gioni'of, constantasignal. strength which coincides? vszitlr the :direction.liniwhichithe antenna which -isri-keyed'(loop;zor frameyiemits nothing. The 1 I sharpness: of theecourselin: this instance maybe pushed toa'higndegree by reducing-the intensityradiotbeaconsofj this type are used Whldh' OllllliIlQj aj veryfisharp"lcourse (say of /z ofgl degree) the v l hase reversal'of the/fields in the 'correspon *atoithe' left; a di rib t 4.5.

suddenly attains its n'raxi rnu'm -value, that 'is, 100.

percentiwvithi'rr' angles that are stillsvery smallE a 7, (forinstance, 'i -3 degrees of the cour se) wherer as inall other azimuths-thekeying percentage or I depth of fthe' signals 1 decreases rapidly; to such an i re'ceivedwheni e in a.1 ha p e saflwh c sei'vir p iecti' a t yv.. f a s t u h u "th a? consists essentially inf defining a radio terns} and Figures 5, 6 and 7 illustratefaeriafar-f rangeinents adapted to produce the radiation pattern of Figs. 2, 3 and/1 respectively 'pli tud e the resultant received has aimaxim nr v ebse' waysa ia.memjaaapiedr'126i with the. aid of two aerials both of which ina directional field distribution, one tn" least, having one QIimOIQ'QiI'BCtlOIlS of zer strength- (so to {speak arr abbreviated looppa rem),-whi1e the other o (contradistini hg fiwtg k ow i he; .ar ll t iiss is axirnu 'when thetransmission of the for err m f'emits minimumsignals (though '2 zfe o s gnals)j in the 'directionsor f {Ifhe'transinission of radio-directionfindin 's'ig .r adiationipatterns could be insured by mea y m i q sin h rt; c. i i

The invention will bernore, easily underst froin the following detailed description by ref= eren'ce to the appended drawingsillustrating 1 ions exemplified embodiments of; the in "imqn,

i ch Fig. 1 represents a'conventio field distr u tion pattern; Fig. 2representsafieldfpat tern 'odified according tothis inventiom Figures 3 are alternative embodiments of fieldp at "1 illustrates the conventional; d gr in orcharacteristic*ofia nondirectional nt and; a *directiona'P loop combination. The

frame: or 1 oo'p; ,-'The' dashed partindicates the points where the-two radiations" are of ejqui keying sincethe signal varies betwee In Fig. 1 the depth of the keying of signals is indicated thus: percent towards or, that is, the course or path covered, since radiation from only one antenna is received 100 percent towards 0x1 direction that is still very close to the course because the latter is very sharp and 2 071 was towards 011, that is to say, 90 degrees of the course. This equation represents the ratio of the change of amplitud e, @ioa or 2 65, to the amplitude ob+oa. This value corresponds to a keying depth around 25%, and this is rather feeble for the ear. Now, it is just this low change in amplitude throughout large angles on either side of the course which it is'the purpose of this invention to remedy.

Figure 2 shows an arrangement according to the invention. The curves I and I still indicate the field distribution produced by the frame antenna, and 2 is the auiziliary. antenna characteristic. "The keying depth or percentages are al'sofindicated in the figure. It will be noticed that they remain very high throughout the space, say,.'above '70 percent, and that the path is very arp. 1 "Figure 3 shows an arrangement in which the path 0:1: is very sharp, while the opposite'course Qiffis considerably wider; still,the depth of keying remains great almost throughout space, except-inthe-neighborhood of 0:13. J; I Figure 4' shows another arrangement covering four equally sharp paths, while resulting throughout space in signals that are keyedat a high modulation percentage. The curves" l and I again sand for the 'fild distribution due ;to the loop antenna. Curves '2' and 2 represent the auxiliary antenna characteristic; it is similar to the frame I, I characteristic, though 'turnedan. angle of 90 degrees, andthe part marked 2' has a pliaseiopposed' to that ofpart '2. 'It can beseen iromFigf lthat the depth of keying is close to 160 percent'throughdut'space.

In all of the Figs. 2, 3, and 4, as will be noted, theinvention has the characteristic feature that any "and every course which is to bemade sharp and clear corresponds, for the field distribution pattern for one antenna, to a region or section with Zero emission, and for the field distribution pattern due to the other antenna to a region of minimum signal strength, whereasfor theother directionsthe field due to'the signal emission from each of the two antennas is of the same order ofintensity, and this brings the keying percentage up'close to'100 percent. I For, a still-better understanding of the situation, it shallfi'nallylbe' eiiplained how such anteens, characteristics maybe obtained, presupposing signal transmissionwith vertical polarization.

'Curvesl, If, of Figs. 2, and are'the chjarac assets oi conventional frames or loops.

gcim' e 2', r g; as obtained by rwaaounetsl disposed in thefdirection inarked. 6513:, being spaced aparta distance slightly less than M2 arid fed in phase, the niiddle b tween the two'doubl'ets been at 0. V r 1 Curve '2', Fig. 3 al'so is obtained byadoubleton dipole fed at 0 and anteriorly of which mounted-yat distance equal to M4 n 0 B, a q doublet designed-to function as a reflectqr.

rn curyes I, I, Fig. 4 are obtainedby two. doublets disposed on the axis 0y beingjgspaced by ways and means well known in the prior art.

The Figures 5, 6 and 7 show aerial systems 7 disposed as explained above for obtaining respectively radiation patterns of Figures 2, 3 and 4.

In all figures identical elements are designated by the same reference letters.

On all the figures, a pair of doublets I0, l0 forms an aerial radiating a field pattern of the shape I, I on Figures 2, 3, 4. These doublets are fed in phase opposition by a transmitter 3 and the feeding phase is inversed bymeans of a switch '4. r

Figure '5, a pair of doublets 20, 20 is disposed on the line Oar at .a distance cl slightly less than M2. The doublets 20, 20' are fed in parallel by the source .3. The diagram ofthis system is shown by 2 on the Figure 2.

Figure 6, a single doublet 2i is located at the centre of the system and fed by the source 3. A

reflecting doublet 21 is located on the line 0:11 at a distance d= \/4 apart. The diagram of the ingdiagrams .ofthe system are indicated in l, I.

and 2,- 2' on the Figure 4.

I claim as my invention: l

1. A radio, beacon system comprising means for producing a first radiation field having two lobes.

of instantaneously opposite polarity and'at least one direction of substantially zero radiation, means for producing a second radiation field the instantaneous .polarity of which isthe same as that of lone of said lobes and the amplitudeof which is less in said direction of zero radiation than in all other directions, and means for causing the alternate reversal of the phase of one of I said radiation'fields to produce an equisignal path in said direction of 'zero radiation.

2. In a radio beacon'i'system comprising two' aerials forpr'oducing radiation fields .of predetermined patterns, one of. said aerials producing a radiation field having twoiobes of instantane-;

ously opposite polarity. to producean axis of zero radiation, means for inversing the phase of the current. energizing one of said a-erials in a pre* determined rhythm to produce .a resultant fi'eld who'se amplitude is-alternatelyequal to the .sum

and the. difierence of said radiation fields, the.

resultant. field being constant ontsaid: axis of zero radiation,- the other. of said aerialsbeing adjusted.

so that the amplitudeof :the other of said fields 1s ,l'essiin the direction .of said :axis of zero radiation than many :other direction', and its instantaneous .piolarity the sameas that of; one of the lobes-of said firstradiation field.

,3- A radio. beacon comprising two pairs of.

dipole aerials disposed in mutually perpendicular planes. the spacing between thefirstaof said pairs;

, being less than a half wave length at the operating frequency, a source of radio frequency currents for energizing one dipole of said first pair in phase with the other dipole of said first pair,

means including said source for energizing one dipole of the second of said pairs in phase opposition to the other dipole of said second pair, and

' being less than a half wave length at the operating frequency and the spacing between the second of said pairs being a half wave length at said operating frequency, a source of radio frequency currents for energizing one dipole of said first pair in phase with the other dipole of said first pair, means including said source for energizing one dipole of the second of said pairs in phase opposition to the other dipole of said second pair, and means for rhythmically reversing the phase of currents energizing one of said pairs of dipole aerials.

5. A radio beacon system, comprising a first aerial for producing a first radiation field having two lobes of instantaneously opposite polarity which produce a direction of zero radiation, a second aerial for producing a second radiation field, means for alternately reversing the polarity of one of said radiation fields to produce an equisignal plane in the direction of said zero radiation, and means associated with said second aerial for reducing the relative amplitude of said second radiation field in said direction of zero radiation.

6. A radio beacon comprising means for producing a first directional radiation field having two lobes of instantaneously opposite polarity, a

pair of antennas spaced apart less than a half,

wave length for producing a second radiation field whose instantaneous polarity is the same' as that of one of said lobes, and means for alternately reversing the relative polarities of said radiation fields.

7. A radio beacon system comprising two aerials for producing radiation fields of mode-- termined patterns, one of said aerials producing a field having two lobes of instantaneously opposite polarity which produce a direction of zero radiation, the other of said aerials producing a.

field whose instantaneous polarity is the same as that of one of said lobes and whose amplitude in said direction of zero radiation is less than in any other direction but greater than zero, and means for alternately reversing the relative polarities of said radiation fields.

YV'ES ROCARD. 

